<meta charset="utf-8">
(#) Deny-listed API

!!! ERROR: Deny-listed API
   This is an error.

Id
:   `DenyListedBlockingApi`
Summary
:   Deny-listed API
Severity
:   Error
Category
:   Correctness
Platform
:   Android
Vendor
:   slack
Identifier
:   slack-lint
Contact
:   https://github.com/slackhq/slack-lints
Feedback
:   https://github.com/slackhq/slack-lints
Min
:   Lint 8.7+
Compiled
:   Lint 8.7+
Artifact
:   [com.slack.lint:slack-lint-checks](com_slack_lint_slack-lint-checks.md.html)
Since
:   0.7.0
Affects
:   Kotlin and Java files, resource files and test sources
Editing
:   This check runs on the fly in the IDE editor
Implementation
:   [Source Code](https://github.com/slackhq/slack-lints/tree/main/slack-lint-checks/src/main/java/slack/lint/denylistedapis/DenyListedApiDetector.kt)
Tests
:   [Source Code](https://github.com/slackhq/slack-lints/tree/main/slack-lint-checks/src/test/java/slack/lint/denylistedapis/DenyListedApiDetectorTest.kt)
Copyright Year
:   2022

This lint check flags usages of APIs in external libraries that we
prefer not to use.

(##) Example

Here is an example of lint warnings produced by this check:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text
src/foo/SomeClass.kt:6:Error: Blocking calls in coroutines can cause
deadlocks and application jank. Prefer making the enclosing function a
suspend function or refactoring this in a way to use non-blocking calls.
If running in a test, use runTest {} or Turbine to test synchronous
values. [DenyListedBlockingApi]
  val result = runBlocking {}
               -----------
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Here is the source file referenced above:

`src/foo/SomeClass.kt`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~kotlin linenumbers
package foo

import kotlinx.coroutines.runBlocking

class SomeClass {
  val result = runBlocking {}
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can also visit the
[source code](https://github.com/slackhq/slack-lints/tree/main/slack-lint-checks/src/test/java/slack/lint/denylistedapis/DenyListedApiDetectorTest.kt)
for the unit tests for this check to see additional scenarios.

The above example was automatically extracted from the first unit test
found for this lint check, `DenyListedApiDetector.coroutineRunBlocking`.
To report a problem with this extracted sample, visit
https://github.com/slackhq/slack-lints.

(##) Including

!!!
   This is not a built-in check. To include it, add the below dependency
   to your project. This lint check is included in the lint documentation,
   but the Android team may or may not agree with its recommendations.

```
// build.gradle.kts
lintChecks("com.slack.lint:slack-lint-checks:0.8.2")

// build.gradle
lintChecks 'com.slack.lint:slack-lint-checks:0.8.2'

// build.gradle.kts with version catalogs:
lintChecks(libs.slack.lint.checks)

# libs.versions.toml
[versions]
slack-lint-checks = "0.8.2"
[libraries]
# For clarity and text wrapping purposes the following declaration is
# shown split up across lines, but in TOML it needs to be on a single
# line (see https://github.com/toml-lang/toml/issues/516) so adjust
# when pasting into libs.versions.toml:
slack-lint-checks = {
    module = "com.slack.lint:slack-lint-checks",
    version.ref = "slack-lint-checks"
}
```

0.8.2 is the version this documentation was generated from;
there may be newer versions available.

[Additional details about com.slack.lint:slack-lint-checks](com_slack_lint_slack-lint-checks.md.html).
(##) Suppressing

You can suppress false positives using one of the following mechanisms:

* Using a suppression annotation like this on the enclosing
  element:

  ```kt
  // Kotlin
  @Suppress("DenyListedBlockingApi")
  fun method() {
     problematicStatement()
  }
  ```

  or

  ```java
  // Java
  @SuppressWarnings("DenyListedBlockingApi")
  void method() {
     problematicStatement();
  }
  ```

* Using a suppression comment like this on the line above:

  ```kt
  //noinspection DenyListedBlockingApi
  problematicStatement()
  ```

* Adding the suppression attribute
  `tools:ignore="DenyListedBlockingApi"` on the problematic XML
  element (or one of its enclosing elements). You may also need to add
  the following namespace declaration on the root element in the XML
  file if it's not already there:
  `xmlns:tools="http://schemas.android.com/tools"`.

  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;java.util.LinkedList xmlns:tools="http://schemas.android.com/tools"
      tools:ignore="DenyListedBlockingApi" ...&gt;
    ...
  &lt;/java.util.LinkedList&gt;
  ```

* Using a special `lint.xml` file in the source tree which turns off
  the check in that folder and any sub folder. A simple file might look
  like this:
  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;lint&gt;
      &lt;issue id="DenyListedBlockingApi" severity="ignore" /&gt;
  &lt;/lint&gt;
  ```
  Instead of `ignore` you can also change the severity here, for
  example from `error` to `warning`. You can find additional
  documentation on how to filter issues by path, regular expression and
  so on
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/lintxml.md.html).

* In Gradle projects, using the DSL syntax to configure lint. For
  example, you can use something like
  ```gradle
  lintOptions {
      disable 'DenyListedBlockingApi'
  }
  ```
  In Android projects this should be nested inside an `android { }`
  block.

* For manual invocations of `lint`, using the `--ignore` flag:
  ```
  $ lint --ignore DenyListedBlockingApi ...`
  ```

* Last, but not least, using baselines, as discussed
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).

<!-- Markdeep: --><style class="fallback">body{visibility:hidden;white-space:pre;font-family:monospace}</style><script src="markdeep.min.js" charset="utf-8"></script><script src="https://morgan3d.github.io/markdeep/latest/markdeep.min.js" charset="utf-8"></script><script>window.alreadyProcessedMarkdeep||(document.body.style.visibility="visible")</script>